Carb Cleaning 101

[Wildkat]

Edited by Crazy Steve. Kat posted this originally (expanding it primarily with pictures on a tip posted by Maans Smit), but the original post only illustrated the late type carbs. So this is being edited/expanded once more to better cover both carb types; the '78-79 and '80-82. Make sure you watch for the differences, and I'd highly recommend that you look here: Carb Identifier Guide first before starting your rebuild if you're not very familiar with these carbs, as well as reading the repair manual section on carbs for additional information. The bulk of the pictures are of the late style carbs and there's not any major differences in the process, so don't be confused if your carb doesn't look exactly like the pic. There's also different schools of thought on whether or not to disassemble the individual carbs off the rack; there's pros and cons for both methods, but this will ultimately be up to you and what condition the carbs are in. This tip also won't get into jetting as that has just too many differences between types and how an individual bike may be set up; jetting guides will be found elsewhere in these tech forums or in the manual. With all this said, let's start....

I've taken the carb cleaning tips here at XS11 starting at the disassembly and added pictures with a few of my own tricks thrown in...

Disassembling the carbs:

I like to work cleanly, so I usually first wash the gunk off the outside of the bank of carbs before I start removing parts. The main idea is to keep the insides of the four carbs separate. They should go back into the same carb they came out of unless a part needs to be replaced. So put them in front of you on a biggish piece of clean paper/cloth the way they sit in front of you on the scoot. No 1 on the left and 4 on the right. Now just turn the bank of carbs upside down.




First you're going to remove the float bowls which are the bottoms of the carbs. I like to first spray all screws/nuts/connections lavishly with PB Blaster or a similar product to make things easy. Note here these are '81-82 type bowls and are side-specific.




Unscrew the four Phillips (or whatever screws - mine came with Phillips and I replaced them with cap/Allen screws) on the corners of each float bowl, then carefully lift each one off. If the gasket comes out without tearing it may be able to be reused, otherwise you'll need a new one. Make sure you keep all internal parts with the carb body it was removed from.




You'll see the float under the float bowl. It is held by a pin which goes through two posts which are part of the carb body. THOSE POSTS BREAK EASILY. Note the small spring clip on the float adjusting tab (look closely); this must be turned towards the pin when reinstalling the float or you might have trouble with the float 'hanging'.




Again, those posts break easily. There's several methods for removing the float pin; you can use a sharp pair of wire cutters as shown but don't pry, just squeeze. You can also use a pair of needlenose pliers and grip the pin head, twisting while gently pulling outwards until the pin comes loose. Some have used a small nail or pin and lightly tapped from the end opposite the head, but use extreme caution if using this method as this is how many posts get broken. If you have an electric soldering iron (the larger the better), applying heat to the post with the pin head on it will help by expanding the aluminum a bit.




Lift the float and float needle up and off the carb. The late carbs have a viton-tipped needle that if the rubber is still resilient can be reused. The early carbs will have a solid-steel needle. If the steel needle isn't worn, it can be polished and reused. Be aware that these are a leading cause of carb leaks, and it's hard to 'eyeball' these to tell if they're good. If you have doubts, I'd recommend replacement of both the needle and the seat.




Ok, several things going on here; the large 'screw' is the main jet. Unscrew it and remember to take its copper/brass washer with it. Above it is the float valve seat. To remove this, take out the screw and the 'Y' clamp that hold it in, then gently grip it with some pliers (if you intend to reuse it) and twist and pull until it's out. There's a o-ring seal on this, replace this if it's more than a year or so old; this is another known leak problem (on the late carbs) as these dry out/shrink. The early carbs will have a hex-head on the seat and are threaded in; simply put the right size socket on it and unscrew it. Both seats will have a small dome-shaped filter on them, don't lose these. If you find much 'stuff' under these, I'd recommend breaking the rack to remove the fuel 'tees' so you can thoroughly clean these passages out. Anything left in here can quickly cause even new valves to leak.




Directly below the now-removed main jet is the pilot jet. On most late carbs, this will be 'open' as seen here. Some '80 carbs may have a rubber plug covering this, if you found the remains of one or it doesn't fit tightly in the hole, you'll need to replace it (for more info on this recheck the linked guide). The '78-79 carbs will have a screw with a thin washer covering this passage, remove the screw.




The standard pilot jets are usually size 42.5, 47.5 if you're working with XJ carbs. NOTE: The pilot jets are brass/copper and the screwdriver slots on top of them strip out easily and then it's hell to get them out. I had to drill one out. So make sure your screwdriver is sharp and fits tightly when you put it in the jet, and put pressure on it and turn slowly. It helps to soak the jets in penetrating oil before you try and get them out. Especially if they haven't been out lately.

Part 2 to follow

[Wildkat]

.... moving on....




Turn the carbs around, put a thick cloth under them so the posts don't break or get damaged, and unscrew the screws holding the tops of the carbs/ diaphragm covers and remove them, the diaphragm springs and the brackets between the carbs.




Slide the diaphragm assembly and needle out. These can be delicate, so handle them with care; the rubber can tear easily, and dropping them on a hard surface can damage the slides enough to make them unusable. After you get them out, hold them up to a strong light and look for holes. Minor pinholes, you may be able to repair them. Big holes or rips, you'll need new ones. This used to be major disaster if you needed to replace these, there's now a reasonably-priced replacement available... look here: Carb Diaphragm Replacement Option Upon reassembly, make certain to match up this 'tab' on the diaphragm with the matching relief in the carb body. Check the jet needles sticking out of the slides; look for bends and heavy wear or 'roughness'. If they're bent, you may be able to straighten them, but badly worn ones should be replaced. Make sure they move freely in their holes; if not, they'll need to be removed and cleaned.




Here's a pic of the '78-79 type jet needles. They assemble in the order shown into the slides, and are held in by the c-clip on the far right. Note that these are adjustable by moving the c-clip on the needle; the '80-82 ones aren't and only have one position. The 'standard' position of the c-clip for the '78-79 is in the middle. The '80-82 are similar, but are removed by taking out the two screws inside the slide as seen in the pic above.




Turn the carb around again and look in the hole where the main jet came out. You'll see the 'needle jet' also known as the emulsion tube. If it pushes out easily into the slide area, remove it. If not, soak it with penetrating oil and tap it out gently from the bottom of the carb, i.e. the main jet hole, with a thin flat screwdriver (round the sides of the hole so you don't damage the thread for the main jet) or a small wooden dowel or pencil. Don't try to pull it out from the slide hole with pliers, you run too much of a risk of damaging the tube. I usually use a small wooden dowel or a pencil to gently tap it through...






The emulsion tube out...




If you look at the inlet/airbox side of the carb body you'll see at 8 o'clock the air pilot jet to be removed and cleaned. Again, make sure the screwdriver fits firmly in the slot. The small jet at the 4 o'clock position isn't removable. The other hole(s) are vents, the large oval one being for the diaphragm/slide, the other one or two for the bowl.




On top of the outlet side of the carb (small mouth which connects to the carb boot/engine) is the idle mixture screw which is the screw you turn to adjust your idle mixture, e.g. when you Colortune. Pictured is the late carb, so this screw is down inside the tower. You may find this hole plugged if the carb hasn't been rebuilt, you need to remove the plug. Drill a small hole in the plug (don't go too deep or you'll damage the screw), then install a small screw in the hole and pull the plug out. After exposing the idle screw, this is the same as all the other jets; the slot is easily stripped, so make sure your screwdriver is sharp and you keep pressure on it while you turn. Some penetrating oil can help. Once you get the screw out, you should find (in order) the screw, a spring, a small washer, and a small o-ring. You'll probably have to pick the washer and/or o-ring out with a paperclip. The o-ring will likely have to be replaced. These parts will come in a rebuild kit, so don't worry about their condition unless you don't plan to buy a kit.

The early carbs are slightly different; the screw is exposed, simply remove it. If the plastic 'anti-tamper' cap is still present, cut that off. All you have is the screw and the spring, no other parts. But these screws are noted for the tips breaking off in the carb body if they're turned in too far, so check for that. The tips can also be damaged, so look for that too. Again, these will be furnished in a rebuild kit. If you have broken tips stuck in the carb bodies, do a forum search for the various methods of removing them. Sometimes they need to be drilled out...

Optional: You can turn each of your idle screws in until they're lightly seated, keeping track of and recording how many turns so when you reinstall you can 'reset' them as they were. This may or may not be helpful, and if you suspect broken tips or they turn very hard, you may want to pass.

Check your choke linkage for operation; if it's frozen or very stiff, you'll probably have to break the rack apart...




... so you can remove the enrichener pistons ('starter plunger') as shown here. Remove these with a socket. These should move freely (except for the slight spring tension) out and snap back in. When disassembling the choke linkage, watch for a small spring and ball in this hole in the number 1 and 4 carbs if you're working with XS carbs; this 'detents' your choke, so try not to lose them. The XJ carbs won't have these holes or the springs/balls. Frozen or stiff linkage is why you find carbs with the choke lever broke off....

If the springs and/or balls get lost or are already missing, you can replace the balls with a common 1/8" diameter ball-bearing. The springs can be ordered new from Yamaha (over $9 each!) but I offer lower-priced alternative replacements. PM me for details... crazy steve

One last thing. There's seals on the throttle shafts, and these do leak on occasion. If you suspect yours are bad, this will require removing the shafts, a rather difficult job. We're not going to cover this here, look in the forum for more specific information. The seals are rather expensive also and won't be included in a rebuild kit.

Ok, the carbs are apart, on to cleaning and reassembly....

[Wildkat]

Upon reassembly...

First, let's talk about cleaning. Number one, a compressed air source is mandatory for cleaning these. You have to be able to blow air through all the various passages to be sure they're clear or you'll likely be wasting your time. Second, you can't get these too clean; the slightest bit of crud left behind can come back and haunt you. Make sure every part, passage, opening, and hole is as clean as possible. There used to be a lot of talk about 'triple-cleaning' these carbs, that was simply because owners weren't getting them clean enough the first two times...

Next, what are you going to use to clean them? This can depend on so many factors; how much do you want to spend, how bad are your carbs, what is available to you? The best/strongest cleaners IMO are either the Yamaha carb dip cleaner (available through your local dealer) or Berrymans Chem-dip (available at most auto parts stores). Price-wise I believe they're about the same (about $25-30 for a gallon container), but there is one major difference. The Yamaha dip is safe on rubber parts, the Berrymans isn't; put rubber parts into that and it will destroy them. I (Crazy Steve) personally use the Berrymans as I haven't found any crud it won't remove. But if you find you need to dip the whole carb body in the Berrymans, you'll need to remove the throttle shafts to protect it's seals (for this, search the forum; it's been covered as to the best methods). From there, some have had success with Pine-sol, Simple Green, spray-can carb cleaner (also very damaging to rubber parts, so don't soak rubber in it) and maybe a few other cleaners, as well as ultrasonic cleaners and heating the cleaning solution. Again, there's been a lot of discussion in the forums as to different cleaning methods, pick one that you think will work for you. I'd highly recommend that you soak all the small metal parts (particularly the jets) in carb cleaner, at least the stuff you can buy in spray cans. You can use gas or thinner to clean the exterior of the carbs. Be safe whatever you use, wear eye protection, etc, etc...

Finally, parts. There's multiple suppliers, some will have everything you need, some will only have certain parts. Favorites on this forum are: http://www.partsnmore.com, http://www.mikesxs.net, http://www.z1enterprises.com, and last but not least, eBay seller 'georgefix' who probably has the best over-all selection of rebuild kits. Do verify that replacement parts are correct before installing (particularly the pilot jets) as there has been issues with incorrect parts being furnished. For best results, most owners report genuine Mikuni jets perform better, so don't be quick to throw away your undamaged stock jets. New Mikuni jets can be purchased at nearly any metric bike dealer as well as online and aren't that expensive.

OK, you've got everything clean enough to pass a white-glove inspection. Reassembly is pretty much just a matter of putting the carbs back together. We'll note the 'special' places that need particular attention, so let's go...




Make sure you take note of the notch and pin when putting the emulsion tube back into place... don't force this.




The tube does NOT go in from this side... It's sitting here for the picture ONLY... (Thank you Don)




The notch in the emulsion tube should fit on this pin.




Also.. make sure you clean this particular tunnel in the float bowl... and it WILL hit you in the eye as it goes through if you aren't careful... DAMHIKIJD

By the way... a MAJOR thanks to John for being so patient in teaching me all of this...

Of course, you'll have to set some stuff; the float levels and a rough 'set' on the idle screws; you should also check for 'bench sync' (making sure the throttle openings are equal), if you've disturbed the linkage or had the carb rack apart, you need to do this; look here: Easy Bench Sync Method

For the floats, if you have brass units, set them to 1" (+/- .040") from the gasket surface to the top of the float with the carb upside down. The plastic floats should be set to .906" (+/- .020"). Note this isn't year-specific, but depends on the float type; if you install plastic floats in early carbs use this number. The '81-82 carbs have a rather involved setting process, you'll find that discussed in the forums as well as in the service manual, but this number will get you close on those. Make sure you check both sides, sometimes the float can be twisted; adjust as needed. In any case, I'd highly recommend referring to the repair manual for specific information and diagrams. You may need to adjust the floats up or down depending on your combination while you tune the bike. Use one of these: Must-Have Tool ... to get your float levels precise; your bike will thank you.

For the idle screws, about 1 1/2 turns out from lightly seated will be a good start for the early carbs, about 2 to 2 1/2 for the late carbs. This will just be a starting point, you'll still need to sync/adjust these for best performance on your bike.

Again, thanks to Wildkat and Maans Smit for the original posts, hope this is helpful!